The present invention relates generally to electronic switches and controls. More specifically, the present invention relates to an electronic interface for controlling the sound of an audio device, such as a CD player.
It is well known in the prior art that such sensors are, essentially, simple electronic sensors that are on the principle of capacitive coupling of an AC voltage source through the human body. Since the human body has a large surface area compared to most electronic buttons and sensors, it will have a larger capacitive coupling to the voltage source than the sensor itself. When a person touches the sensor, such as by a finger, the net result is that the voltage signal on the sensor is increased due to the better capacitive coupling.
This technology is applicable to devices which are plugged into a mains AC source. In America, the standard is 120 VAC and the frequency is 60 Hz. In many locations this standard can be different. Some locations may have higher or lower AC voltages and may hove higher or lower frequencies. In the context of touch sensors, it is assumed that such an AC source may vary between, for example, about 90 VAC and about 264 VAC worldwide and between about 47 Hz and about 63 Hz in frequency. It should be understood that these are just examples of voltages and frequencies that can accommodate a touch sensor and that other ranges of voltages and frequencies can be used.
In the prior art, the operability of touch sensor technology depends very heavily on a controlled environment with known parameters. In such an environment, it is very simple to build a sensor that can determine if someone has touched it. An example of such a controlled environment is as follows:                1) No other nearby devices or wiring will add or subtract significantly to the AC voltage coupled to the person who touches the sensor or the sensor itself;        2) The device itself emits a known AC mains signal;        3) The device is always installed in the same type of location; and        4) It is not possible for the person to ground his/her body.        
An example of a such a device that would meet these criteria is an automatic teller machine. The device is stand-alone and there are no other nearby devices. The device will always have roughly the same AC mains signal emitted as long as it is mass produced. The installer of the device most likely will ensure that the locations always have similar wiring. The device is made of plastic so a person can't ground his body.
As can be understood, such a controlled environment cannot always be achieved and, therefore, restricts the installation options for the touch sensor.
This is a significant drawback for known touch sensor devices. For example, a useful environment and application for a touch sensor is consumer electronic equipments, such a stereo equipment and disc jockey (“DJ”) equipment. DJ equipment, an ideal environment for use of touch sensors, is particularly problematic because the equipments is frequently moved from location to location and is subject to vastly differing environments with different voltage supplies, different levels of static electricity, for example. As a result, use of a touch sensor in DJ equipment is not practical because there are too many variables and performance of the touch sensor will be inferior and, therefore undesirable.
Many attempts have been made in the prior art to address the shortcomings of known touch sensors when used in DJ equipment and other electronics. For example, the equipment has been placed on a metal surface for the purposes of attempting to shield the signal from AC sources. If the equipment with the touch sensor is placed in a high static environment, often the DJ will pick up a static signal which is far greater than the AC source pickup resulting in erratic touch sensor performance. Also, it is common for such equipment to be placed next to a mixer which results in the DJ frequently grounding his/her body through the mixer when working with a CD player and mixer together which again makes use of a touch sensor very difficult. Furthermore, the use of equipment in many places through the world, each with different AC mains grounding and different proximity to AC power sources, makes it very difficult to achieve satisfactory touch sensor performance.
Therefore, in view of the concerns discussed above, it would be desirable for a touch sensor that has high performance regardless of the operating environment. It is also desirable for a touch sensor to be resistance to environmental static electricity and still perform as desired. Further, is also desirable for a touch sensor to be resistant to periodic grounding by the user. It is further desirable for the touch sensor that can perform as desired even when placed close to an AC source.